”Australia’s First 4 Billion Years” delivers the joy of geology.

It’s the geologist’s refrain: rocks tell stories. Geologists don’t (usually) get excited about a chunk of sandstone just because it’s sandy. It’s the secrets it holds—secrets about a world in the past that we can never visit, even as we stand on its consequences.

“Australia’s First 4 Billion Years," a four-part series that begins April 10th on NOVA, recounts the tale of Earth’s history the right way—by letting the rocks tell it. And it does so without even leaving the land down under (save a short stop in New Zealand).

That’s not a limitation, it’s a strength. It allows the program to hone in on details that many won't have heard before, rather than providing a montage of interesting events around the world—an approach that usually yields only the most familiar ones. The program builds an appreciation for the landscape, too, by allowing you to more fully explore the rich history of a region. Besides, Australia’s geology lays bare an impressive amount of geologic time. You could do much worse as far as locations go.

In the first episode, Richard Smith (your guide to all rocks Australian) sets up the series as an adventure in time travel. Using travel down the road as an analogy for moving backward in time, we get some feeling for the vast amounts of time between key events in Earth’s past. Arriving at the formation of the Solar System, the series begins its march forward.

Australia is a great place to talk about the early Earth. It’s home to the oldest things yet discovered (the 4.4 billion-year-old Jack Hills zircons), and stromatolites—the distinctive colonies of archea that appeared 3.5 billion years ago—which can still be seen forming in Shark Bay.

Since the rock record becomes sparse when you get that far back in time, the first program handily covers about 4 billion years. The rest of the series details the last 500 million years, over which organisms have (for the most part) become progressively more familiar.

The second episode looks at the evolution of fish—their invasion of the land and the invertebrates that beat them there, all of which took place on an Australia that bears no resemblance to the one we know. Australia is currently arid and isolated, which makes it even more fun to envision what it looked like when it was once the seafloor. There is also evidence of an ice sheet that covered Australia when it was part of a massive assembly of all the continents.

Following the extinction at the end of the Permian (the Great Dying), the third episode enters the age of everyone’s favorite prehistoric creatures—the dinosaurs. Australia has not been known for its dinosaur fossils, but recent discoveries have provided more than enough treasures to explore. That includes some absolutely gorgeous trackways—one of which may even represent a herd fleeing a stalking predator (though a nice article on the NOVA website explains there is some disagreement about this).

But the dinosaurs couldn’t outrun extinction, of course, which paved the way for the mammal revolution. The final episode focuses on the truly unique fauna that evolved after Australia cut its last ties with Pangaea—from marsupials (kangaroos, of course) to the egg-laying monotremes (echidnas and platypuses). During the glacial periods of the last few million years, megafauna—including huge kangaroos that stood nearly seven feet tall—could have been found in Australia, but may have disappeared at the hands of a vagabond species that showed up some 50,000 years ago. Those humans left their mark on the Australian continent as well, including preserved tracks and remarkable artwork.

The series ends with a little contemplation along those lines—the stories the rocks will tell of humans in the distant future. From mining to agriculture to extinctions to climate change, the human species has more power, in a way, than any species before it. We are altering the planet in a myriad of ways, and as Richard Smith puts it, “The geological extinction record shows we do so at our peril.”

Throughout, the series is well put together. The visuals (both real and computer-generated) are beautiful, and the stories are clearly and engagingly told. There’s plenty to discover, even if the major scenes in the play are familiar to you. And most importantly, it’s fun—the ratio of “wow!” to “how” is pretty laid-back. If you want to kick back and catch up on the last four-and-a-half billion years, this series won’t disappoint.

48 Reader Comments

I am very very picky about the science/nature documentaries I watch, since I am too jaded to respond well to the 'dramatic narrative' documentary producers often artificially slap together out of often unrelated footage.

PBS's NOVA series hardly ever bothers me in that sense. Really looking forward to this one.

NOVA is my favorite science show. I get sick of the amped-up artificial drama of anything on Discovery or History. It's hard to find anything on those channels anymore anyways, but the few actual science shows that do pop up on there tend to feel like the producers have aspirations of being the next Michael Bay.

I mean, seriously. Geology is very interesting, but it isn't exactly exciting, for the most part. Not everything has to be a top-ten list of the most whizz-bang effects producible on television.

That’s not a limitation, it’s a strength. It allows the program to hone in on details that many won't have heard before, rather than providing a montage of interesting events around the world—an approach that usually yields only the most familiar ones. The program builds an appreciation for the landscape, too, by allowing you to more fully explore the rich history of a region.

True that. It seems that nature/natural history shows have a habit of hitting the same places over and over. There are already countless shows on the Great Barrier Reef, the Serengeti, the Amazon Rainforests. Not that these places aren't interesting, but there definitely is room to expand on documenting the rest of the world. I am in full agreements that a show that focuses just on the geologic/natural Australia would be very interesting.

On a different note, I have only been getting into geology probably in the past year. In the US there is a nice series of books called "Roadside Geology" that includes a guide for the majority of the states. If anyone has an interest in learning how your home state came to be, these are a good place to start.

«We are altering the planet in a myriad of ways, and as Richard Smith puts it, “The geological extinction record shows we do so at our peril.”»

You know, our atmosphere is rich in oxygen only because the cyanobacteria altered the planet in a massive way. All of us mammals owe our very lives to these planet alterers.

It just gets tiresome to hear that everything we do must be a "peril". How about celebrating our success as a species from time to time instead of inserting foreboding "peril" political messaging into everything, even a brain-dead geohistory documentary?

It just gets tiresome to hear that everything we do must be a "peril". How about celebrating our success as a species from time to time instead of inserting foreboding "peril" political messaging into everything, even a brain-dead geohistory documentary?

I think celebrating our successes would be great! Especially since in my view part of the reason we are still altering a lot of already useful and functioning land into something less so is because we can't seem to realize how successful we have been.

Edit: I would like to add, is the documentary "brain-dead" because it is light on facts and information, or just because it doesn't agree with what you believe?

Adding an article like this, and the tomato article, and the review of River of Stars to the usual array of consumer (and professional!) electronics news makes Ars a really, really great site to spend time on.

It just gets tiresome to hear that everything we do must be a "peril". How about celebrating our success as a species from time to time instead of inserting foreboding "peril" political messaging into everything, even a brain-dead geohistory documentary?

I celebrate the success of the government funded climate science conspiracy that keeps your articulate and cogent opinions marginalized.

On the topic of "shows about the natural history of our planet", How The Earth Was Made is pretty great. It genuinely got me excited about geology, a topic I previously thought was pretty dull. There are a few free episodes on the site, and I can especially recommend the ones on "the deepest place on earth" (Mariana trench) and "driest place on earth" (Atacama desert). The narrator explains and connects together the evidence in a way that is thoughtful and convincing.

The show was formerly on Netflix and I hope they bring it back, because I didn't finish all of it...

EDIT: I'll also recommend Prehistoric Disasters, which is entertaining and looks great, though I'm not sure how well-corroborated the claims are. Still, it's eye-opening to see the dramatic and violent events that may have shaped a younger Earth.

I've always liked Nova, except when the show veers into politics and pretends it is science. But this seems like a fun series to watch--so I'll look for it later on DVD or Netflix or Hulu (I'm not much for television these days.)

Quote:

But the dinosaurs couldn’t outrun extinction, of course, which paved the way for the mammal revolution.

Here's hoping the series is heavy on the geology and light on evolutionary theory. Your statement above brings to the fore a question I've never seen answered well before (because I don't think there is an answer.)

Say that the dinosaurs were exterminated in part by an extraterrestrial event like an asteroid collision, and then disease and famine finished the job. When the skies cleared and conditions returned to as "normal" as they might ever be for the support of life, why didn't the dinosaurs simply "re-evolve"--ie, why didn't they just come back? I mean, for one thing, their genetic material was abundant probably everywhere, and secondly, if we say that the mandate for evolutionary progress is survival, then the dinosaurs (and much of the plant life the dinosaurs were accustomed to) were enormously gifted by nature in the survival department.

An event like an asteroid impact, of course, would have zero relevancy to species survival from an evolutionary point of view, since extraterrestrial events are outside the scope of the evolutionary paradigm--ie, "nature" would not care (or "know") if the dinosaurs were extinguished by an asteroid since that would have no bearing on their naturally selected abilities to survive on the face of the planet. As well, even with developed brains, were mankind today faced with an oncoming asteroid of that size--even with a decade-long advanced warning--there would be little to nothing that our brains would produce that would enable us to fare any better than did the dinosaurs in the aftermath of such a collision--a true extinction event.

So...why would a wholly different order of plant and animal life "materialize" in the wake of the asteroid extinction event? It isn't clear to me that evolutionary theory can answer this question, as natural selection certainly would not call for it.

Posts like this must absolutely send science pedagogues spiraling into destructive existentialist crises.

I've always liked Nova, except when the show veers into politics and pretends it is science. But this seems like a fun series to watch--so I'll look for it later on DVD or Netflix or Hulu (I'm not much for television these days.)

Quote:

But the dinosaurs couldn’t outrun extinction, of course, which paved the way for the mammal revolution.

Here's hoping the series is heavy on the geology and light on evolutionary theory. Your statement above brings to the fore a question I've never seen answered well before (because I don't think there is an answer.)

WaltC wrote:

Say that the dinosaurs were exterminated in part by an extraterrestrial event like an asteroid collision, and then disease and famine finished the job. When the skies cleared and conditions returned to as "normal" as they might ever be for the support of life, why didn't the dinosaurs simply "re-evolve"--ie, why didn't they just come back? I mean, for one thing, their genetic material was abundant probably everywhere, and secondly, if we say that the mandate for evolutionary progress is survival, then the dinosaurs (and much of the plant life the dinosaurs were accustomed to) were enormously gifted by nature in the survival department.

An event like an asteroid impact, of course, would have zero relevancy to species survival from an evolutionary point of view, since extraterrestrial events are outside the scope of the evolutionary paradigm--ie, "nature" would not care (or "know") if the dinosaurs were extinguished by an asteroid since that would have no bearing on their naturally selected abilities to survive on the face of the planet. As well, even with developed brains, were mankind today faced with an oncoming asteroid of that size--even with a decade-long advanced warning--there would be little to nothing that our brains would produce that would enable us to fare any better than did the dinosaurs in the aftermath of such a collision--a true extinction event.

Someone who knows the K/T period better than I can probably help me out, but I believe a lot of the dinosaurs were already starting to evolve into species that didn't appear to be "stereotypical dinosaurs" long before the K/T extinction event. Couple this with the fact that the landmasses were slowly moving around and changing climates around there is ample change in environment for species not to return to Cretaceous body types.

If something impacts and changes the environment, it is absolutely relevant to evolution. AN asteroid collision is a disturbance of an incredible magnitude, but it is still another environmental disturbance. Outer space is just part of the continuum of environment and habitat. Excluding causes of environmental change just because they do not begin on the planet doesn't really have any basis. If it caused some change in an organism's environment, then it will be something evolutionary mechanisms will act upon.

Say that the dinosaurs were exterminated in part by an extraterrestrial event like an asteroid collision, and then disease and famine finished the job. When the skies cleared and conditions returned to as "normal" as they might ever be for the support of life, why didn't the dinosaurs simply "re-evolve"--ie, why didn't they just come back? I mean, for one thing, their genetic material was abundant probably everywhere, and secondly, if we say that the mandate for evolutionary progress is survival, then the dinosaurs (and much of the plant life the dinosaurs were accustomed to) were enormously gifted by nature in the survival department.

The rock that kissed Chicxulub obliterated nearly as many plant species as it did animal species, hence the environment that the dino's specialized for simply no longer existed.Larger creatures were even more affected than smaller ones.

WaltC wrote:

So...why would a wholly different order of plant and animal life "materialize" in the wake of the asteroid extinction event? It isn't clear to me that evolutionary theory can answer this question, as natural selection certainly would not call for it.

Like bureaucracy, life expands to fill every available niche, mammals would simply have pressured any remaining dino species into extinction.(on a side note, fungi & ferns seem to do particularly well after asteroid impacts for relatively obvious reasons, but just dont seem to have the long term staying power.)

I've always liked Nova, except when the show veers into politics and pretends it is science. But this seems like a fun series to watch--so I'll look for it later on DVD or Netflix or Hulu (I'm not much for television these days.)

Quote:

But the dinosaurs couldn’t outrun extinction, of course, which paved the way for the mammal revolution.

Here's hoping the series is heavy on the geology and light on evolutionary theory. Your statement above brings to the fore a question I've never seen answered well before (because I don't think there is an answer.)

Say that the dinosaurs were exterminated in part by an extraterrestrial event like an asteroid collision, and then disease and famine finished the job. When the skies cleared and conditions returned to as "normal" as they might ever be for the support of life, why didn't the dinosaurs simply "re-evolve"--ie, why didn't they just come back? I mean, for one thing, their genetic material was abundant probably everywhere, and secondly, if we say that the mandate for evolutionary progress is survival, then the dinosaurs (and much of the plant life the dinosaurs were accustomed to) were enormously gifted by nature in the survival department.

An event like an asteroid impact, of course, would have zero relevancy to species survival from an evolutionary point of view, since extraterrestrial events are outside the scope of the evolutionary paradigm--ie, "nature" would not care (or "know") if the dinosaurs were extinguished by an asteroid since that would have no bearing on their naturally selected abilities to survive on the face of the planet. As well, even with developed brains, were mankind today faced with an oncoming asteroid of that size--even with a decade-long advanced warning--there would be little to nothing that our brains would produce that would enable us to fare any better than did the dinosaurs in the aftermath of such a collision--a true extinction event.

So...why would a wholly different order of plant and animal life "materialize" in the wake of the asteroid extinction event? It isn't clear to me that evolutionary theory can answer this question, as natural selection certainly would not call for it.

Simple answer is there was a certain set of conditions that allowed for the evolution of dinosaurs when they did evolve that did not exist after they went extinct. I don't know the specifics (even though I have a strong background in biology) but I'd say the very existence of mammals this "second" time around would curtail the evolution of extremely large reptiles. Competition for resources plus new types of predators can have a huge impact on the direction things would go.

Adding an article like this, and the tomato article, and the review of River of Stars to the usual array of consumer (and professional!) electronics news makes Ars a really, really great site to spend time on.

The Verge also verges (what a punny thread this has become) into other areas, but to be honest, I often find their non-tech stories to be somewhat lacking. But those folks are younger, and they probably all live in Williamsburg and buy lots of "artisanal" foods and such and enjoy dubstep, so there you go. Thankfully Ars is dominated by Chicagoans, so we can avoid most of the hipster-y stuff when they verge outside the tech realm. This is absolutely a good thing.

Although I think I might find an "Aurich goes off the internet for a year" series entertaining. Or maybe Peter, that would be good too. But if it's Aurich, then we'd have sketches on all the articles, which would probably be pretty cool.

Regarding the nature doc, it totally blows my mind that 46% of people in this country would watch that show and have to conclude it's all made up since the world is only 10,000 years old:

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Forty-six percent of Americans believe in the creationist view that God created humans in their present form at one time within the last 10,000 years. The prevalence of this creationist view of the origin of humans is essentially unchanged from 30 years ago, when Gallup first asked the question.

...a question I've never seen answered well before (because I don't think there is an answer.)

There are answers (theories), but I can't say whether you would consider the question well-answered, and they would encompass about three semesters of paleontology classes.

Quote:

Say that the dinosaurs were exterminated in part by an extraterrestrial event like an asteroid collision, and then disease and famine finished the job. When the skies cleared and conditions returned to as "normal" as they might ever be for the support of life, why didn't the dinosaurs simply "re-evolve...

Even when conditions seem favorable re-evolution seems to be extremely rare. I guess in a grossly oversimplified way you could say that it would be most likely where a creature that's already close enough (in a genetic sense) is in the right place at the right time when its former niche is vacated by some other creature(s).

Quote:

An event like an asteroid impact, of course, would have zero relevancy to species survival from an evolutionary point of view, since extraterrestrial events are outside the scope of the evolutionary paradigm--ie, "nature" would not care (or "know") if the dinosaurs were extinguished by an asteroid since that would have no bearing on their naturally selected abilities to survive on the face of the planet.

Actually, such an event is entirely relevant. Evolution seems to be intensely slow, and more or less random during times of stability. A major extraterrestrial event is exactly the kind of motivator that tends to kick evolution into high gear. When a lot of habitats suddenly appear, disappear, or become vacant there is a lot of opportunity for expansion and speciation.

Quote:

So...why would a wholly different order of plant and animal life "materialize" in the wake of the asteroid extinction event? It isn't clear to me that evolutionary theory can answer this question, as natural selection certainly would not call for it.

They didn't really "materialize". The mammals, etc. were already pretty well established at that point. The extinction of a lot of large predators and competitors just allow them to flourish. Natural selection as presented by Darwin tends to be overstated, because it's famous. There are many other mechanisms for evolution that just don't get as much press, because they're moslty boring.

I've always liked Nova, except when the show veers into politics and pretends it is science. But this seems like a fun series to watch--so I'll look for it later on DVD or Netflix or Hulu (I'm not much for television these days.)

Quote:

But the dinosaurs couldn’t outrun extinction, of course, which paved the way for the mammal revolution.

Here's hoping the series is heavy on the geology and light on evolutionary theory. Your statement above brings to the fore a question I've never seen answered well before (because I don't think there is an answer.)

Say that the dinosaurs were exterminated in part by an extraterrestrial event like an asteroid collision, and then disease and famine finished the job. When the skies cleared and conditions returned to as "normal" as they might ever be for the support of life, why didn't the dinosaurs simply "re-evolve"--ie, why didn't they just come back? I mean, for one thing, their genetic material was abundant probably everywhere, and secondly, if we say that the mandate for evolutionary progress is survival, then the dinosaurs (and much of the plant life the dinosaurs were accustomed to) were enormously gifted by nature in the survival department.

An event like an asteroid impact, of course, would have zero relevancy to species survival from an evolutionary point of view, since extraterrestrial events are outside the scope of the evolutionary paradigm--ie, "nature" would not care (or "know") if the dinosaurs were extinguished by an asteroid since that would have no bearing on their naturally selected abilities to survive on the face of the planet. As well, even with developed brains, were mankind today faced with an oncoming asteroid of that size--even with a decade-long advanced warning--there would be little to nothing that our brains would produce that would enable us to fare any better than did the dinosaurs in the aftermath of such a collision--a true extinction event.

So...why would a wholly different order of plant and animal life "materialize" in the wake of the asteroid extinction event? It isn't clear to me that evolutionary theory can answer this question, as natural selection certainly would not call for it.

Wow. So much fail in one post. It would be difficult to point out all of the inaccuracies, but let me point out a few.

Animals don't grow out of genetic material lying around on the ground. You should probably have a talk with your parents about the birds and the bees sometime soon.

Dinosaurs evolved over a period of about 160 million years. For them to "re-evolve", ALL of the chance conditions which were present during that time would have to play out exactly the same, over another 160 million years.

Not all dinosaurs became extinct. Avian dinosaurs survived, continued to evolve, and became the birds we see and interact with today.

The Small mammals had already been present and evolving for a long time before the CT boundary event. They were there to fill the empty niches which allowed them to flourish and evolve further.

Don't worry too much, though. It's good when you have questions. Sometime in the next few years evolution will be covered by one of your school teachers. It's an exciting topic and you will enjoy it when you are old enough.

why didn't the dinosaurs simply "re-evolve"--ie, why didn't they just come back? I mean, for one thing, their genetic material was abundant probably everywhere, and secondly, if we say that the mandate for evolutionary progress is survival, then the dinosaurs (and much of the plant life the dinosaurs were accustomed to) were enormously gifted by nature in the survival department.

How would horizontal gene transfer from dead carcases bring a species back? Extinct is extinct.

Note that those dinosaurs small enough to survive the ash winter did, as birds. And while the conditions were favorable, some birds achieved megafauna size.

Don't worry too much, though. It's good when you have questions. Sometime in the next few years evolution will be covered by one of your school teachers. It's an exciting topic and you will enjoy it when you are old enough.

Say that the dinosaurs were exterminated in part by an extraterrestrial event like an asteroid collision, and then disease and famine finished the job. When the skies cleared and conditions returned to as "normal" as they might ever be for the support of life, why didn't the dinosaurs simply "re-evolve"--ie, why didn't they just come back?

Come back from what? The archosaur species that the first dinosaur species descended from were already long gone by the end of the Triassic. Birds had already diverged pretty far from their saurian ancestors by the end of the Cretaceous, and mammals were descended from a different group of critters entirely. You simply didn't have anything that dinosaurs (at least in the form we're familiar with) could evolve from anymore.

Some population of mammals will eventually spawn daughter populations that are the first steps towards a post-mammal group, and mammals as we understand the term will eventually go extinct, while the post-mammal species continue to diversify. Whatever those post-mammal species eventually become, they very likely will not turn into dinosaurs as we know them.

Quote:

I mean, for one thing, their genetic material was abundant probably everywhere, and secondly, if we say that the mandate for evolutionary progress is survival, then the dinosaurs (and much of the plant life the dinosaurs were accustomed to) were enormously gifted by nature in the survival department.

Except when it came to earth-shattering kabooms, obviously. By that metric, you could argue that mammals, birds, many reptiles, fish, etc., were even more gifted in the survival department. And remember, "dinosaurs" is an umbrella term; hundreds, if not thousands, of individual dinosaur species arose and went extinct all through the Mesozoic; no one species made it all the way from beginning to end.

Quote:

An event like an asteroid impact, of course, would have zero relevancy to species survival from an evolutionary point of view, since extraterrestrial events are outside the scope of the evolutionary paradigm--ie, "nature" would not care (or "know") if the dinosaurs were extinguished by an asteroid since that would have no bearing on their naturally selected abilities to survive on the face of the planet.

On the contrary, it's entirely relevant. The asteroid impact led to rapid and radical changes in the environment worldwide, changes to which none of the remaining dinosaur species could adapt quickly enough to survive (unlike some number of bird and mammal (and reptile and fish and plant and ...) species). That's why they went extinct.

As a counterpoint, I've seen it argued that human intelligence evolved as a response to rapid (in the geologic sense) and repeated climate changes across the African continent 3 to 4 million years ago.

Quote:

As well, even with developed brains, were mankind today faced with an oncoming asteroid of that size--even with a decade-long advanced warning--there would be little to nothing that our brains would produce that would enable us to fare any better than did the dinosaurs in the aftermath of such a collision--a true extinction event.

I don't know; ugly as the Chixhulub impact was, it didn't kill everything. It's possible that some group of humans located far enough away from the impact with access to enough resources to hunker down for a few decades or so would survive.

Quote:

So...why would a wholly different order of plant and animal life "materialize" in the wake of the asteroid extinction event? It isn't clear to me that evolutionary theory can answer this question, as natural selection certainly would not call for it.

Numerous bird and mammal species were already around well before the Chixhulub impact, but were not very prevalent or diverse because most of the ecological niches were already filled by the dinos. After the dinos went extinct, birds and mammals had more room to expand and diversify. They didn't materialize out of nowhere.

Same thing for the plants; those species that were able to survive the K-T event suddenly had much less competition, and were able to thrive.

It just gets tiresome to hear that everything we do must be a "peril". How about celebrating our success as a species from time to time instead of inserting foreboding "peril" political messaging into everything, even a brain-dead geohistory documentary?

I think celebrating our successes would be great! Especially since in my view part of the reason we are still altering a lot of already useful and functioning land into something less so is because we can't seem to realize how successful we have been.

Edit: I would like to add, is the documentary "brain-dead" because it is light on facts and information, or just because it doesn't agree with what you believe?

Yes, it's odd isn't it how the same people who say "there's no way we could be changing the Earth- it's too big and we are too small" are often the same technological triumphalists who say "humans can do anything- if we mess up the Earth, we'll just fix it up".

Don't worry too much, though. It's good when you have questions. Sometime in the next few years evolution will be covered by one of your school teachers. It's an exciting topic and you will enjoy it when you are old enough.

Animals don't grow out of genetic material lying around on the ground.

Have you learned nothing from Prometheus? A living organism and a little black goo...

Joking aside, there are interesting concepts in the thread of life only arising from other living organisms (biogenesis) and from inorganic material under circumstances we do not yet understand (abiogenesis). Theoretically, animals can (and have) grown out of material lying around on the ground, or rather, organic molecules in the presence of some catalyzing agent (electricity, God, etc.) formed protocells which subsequently evolved into animals. Or something.

Your question has been answered well several times you have either ignored it or more likely not looked for the answer. First and foremost the dinosaurs didn't go completely extinct, a sub-set did evolve, into birds. Mammals as well did not "materialize" mammalian species did in fact co-exist with dinosaurs.

The asteroid impacts immediate effects are still in some debate ranging from climate change leading to food shortages to effectively the entire sky the world over filling with burning ash and the entire surface of the earth burning.

Regardless such an event would have a much more dramatic effect on large and highly specialized animals than on smaller or opportunistic ones. smaller organisms could more easily evade the direct cataclysmic events (as well as out breed the catastrophe as a smaller creature has a much lower time scale from birth to sexual maturity). When the darkened skys led to massive food shortages (Less sunlight less plantlife) large creature would have difficulty in getting sufficient calories to sustain thier size. This puts evolutionary pressure on smaller organisms. Specialized animals would likewise have difficulty getting enough of the food they required whether that be ferns, high leaves, or meat form large herbivores. Opportunistic organisms would eat whatever came there way and thus be more successful.

As for why the dinosaurs didn't simply re-establish their dominance and re-evolve once more quite simply the pressures were no longer the same. The small dinosaurs who did survive were in direct competition with mammals (the dinosaurs precursors were not) and the climate and other environmental factors were also drastically different. The new environment and competition was one the mammals were better suited to take advantage of, fur helps with the colder temperatures (hence why the surviving dinosaurs selected for feathers), dominance of small opportunistic feeders means that live birth and rearing of young is much more successful than eggs unless of course you hide the eggs in difficult to reach places such as those accessible only via flight.

Solid evolutionary theory actually checks out surprisingly well against what we know from the geologic record of conditions following the impact and the ensuing mass extinctions.

WaltC wrote:

I've always liked Nova, except when the show veers into politics and pretends it is science. But this seems like a fun series to watch--so I'll look for it later on DVD or Netflix or Hulu (I'm not much for television these days.)

Quote:

But the dinosaurs couldn’t outrun extinction, of course, which paved the way for the mammal revolution.

Here's hoping the series is heavy on the geology and light on evolutionary theory. Your statement above brings to the fore a question I've never seen answered well before (because I don't think there is an answer.)

Say that the dinosaurs were exterminated in part by an extraterrestrial event like an asteroid collision, and then disease and famine finished the job. When the skies cleared and conditions returned to as "normal" as they might ever be for the support of life, why didn't the dinosaurs simply "re-evolve"--ie, why didn't they just come back? I mean, for one thing, their genetic material was abundant probably everywhere, and secondly, if we say that the mandate for evolutionary progress is survival, then the dinosaurs (and much of the plant life the dinosaurs were accustomed to) were enormously gifted by nature in the survival department.

An event like an asteroid impact, of course, would have zero relevancy to species survival from an evolutionary point of view, since extraterrestrial events are outside the scope of the evolutionary paradigm--ie, "nature" would not care (or "know") if the dinosaurs were extinguished by an asteroid since that would have no bearing on their naturally selected abilities to survive on the face of the planet. As well, even with developed brains, were mankind today faced with an oncoming asteroid of that size--even with a decade-long advanced warning--there would be little to nothing that our brains would produce that would enable us to fare any better than did the dinosaurs in the aftermath of such a collision--a true extinction event.

So...why would a wholly different order of plant and animal life "materialize" in the wake of the asteroid extinction event? It isn't clear to me that evolutionary theory can answer this question, as natural selection certainly would not call for it.

A good sized male Red easily gets to six feet, 180 lbs, and can jump 10 metres.

Not to mention being both adorable and delicious.

Extinct Australian marsupials are much more interesting than that - ten foot tall (200 kg) kangaroos, wombats as big as a rhino, half-ton flightless birds standing 3 metres tall - down to the tiny long-tailed plaginale that still live today in the far north (a really big one can reach 6 grams, with a head five times wider than it is deep).